Friday, May 28, 2010

Why the Increase in Hurricanes this year?

If you are making a trip to the east coast from Myrtle Beach to the Outer Banks to Hilton Head down to Miami, pay attention to the tropical forecast this summer and fall as tropical storms will be a plenty.

Why is season going to be so active? Here is a technical/sciency peek into how the experts come up with their HURRICANE FORECASTS:

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The first factor is whether an EL NINO or LA NINA is present. Remember that EL NINO/LA NINAs are changes in sea surface temperatures in the Pacific Ocean. These changes alter the position and direction of the jet stream in the atmosphere either BREAKING APART tropical systems of allowing them to BUILD INTO HURRICANES.

Last year, EL NINO BROKE APART THE STORMS.

This year without EL NINO, and with LA NINA rapidly developing, the sheer is weak so the environment is very strong for TROPICAL STORM DEVELOPMENT. Storms are steered right into the Caribbean.

The next factor is the temperature of the Atlantic Ocean. For the last several months, the Atlantic SEA SURFACE TEMPERATURES have been at levels not seen in decades. Remember last winter's cold spells? That same arctic pattern responsible for our winter cold drove the Bermuda High south allowing the ocean to heat up to near record levels. The red shades on the map below show the warmer than normal water in the central Atlantic.

One other factor that will be present in hurricane forecasts for years to come has to do with a decadal cycle of high and low hurricane frequency. The ATLANTIC MULTIDECADAL OSCILLATION or the AMO is a cyclical pattern of sea surface temperature completing a cold/warm/back to cold cycle every 70 years or so. Since 1995, we have been in a warm cycle. Here is the cycles since 1860.

There are also US LANDFALL HURRICANE TRENDS that correlate to the AMO. Check these out below. The left image is a reflection of the current WARM CYCLE. We can expect more US landfall hurricanes in a WARM AMO cycle which will more than likely continue for the next 20 years.

Factor in a turbulent and strong LOOP CURRENT shown here...

which has a history of rapidly intensifying hurricanes like Katrina and Rita in 2005...